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Date:   Thu, 12 Dec 2019 13:20:53 +0100
From:   Greg KH <gregkh@linuxfoundation.org>
To:     Heikki Krogerus <heikki.krogerus@linux.intel.com>
Cc:     zhong jiang <zhongjiang@huawei.com>, linux@roeck-us.net,
        linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] usb: typec: fusb302: Fix an undefined reference to
 'extcon_get_state'
Message-ID: <20191212122053.GA1541203@kroah.com>
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 <5DF20B18.4020601@huawei.com>
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On Thu, Dec 12, 2019 at 01:18:05PM +0200, Heikki Krogerus wrote:
> On Thu, Dec 12, 2019 at 05:40:40PM +0800, zhong jiang wrote:
> > On 2019/12/12 17:28, Greg KH wrote:
> > > On Thu, Dec 12, 2019 at 05:15:28PM +0800, zhong jiang wrote:
> > >> On 2019/12/12 17:01, Heikki Krogerus wrote:
> > >>> On Thu, Dec 12, 2019 at 03:34:23PM +0800, zhong jiang wrote:
> > >>>> Fixes the following compile error:
> > >>>>
> > >>>> drivers/usb/typec/tcpm/fusb302.o: In function `tcpm_get_current_limit':
> > >>>> fusb302.c:(.text+0x3ee): undefined reference to `extcon_get_state'
> > >>>> fusb302.c:(.text+0x422): undefined reference to `extcon_get_state'
> > >>>> fusb302.c:(.text+0x450): undefined reference to `extcon_get_state'
> > >>>> fusb302.c:(.text+0x48c): undefined reference to `extcon_get_state'
> > >>>> drivers/usb/typec/tcpm/fusb302.o: In function `fusb302_probe':
> > >>>> fusb302.c:(.text+0x980): undefined reference to `extcon_get_extcon_dev'
> > >>>> make: *** [vmlinux] Error 1
> > >>> There are stubs for those functions so that really should not be
> > >>> happening. I can not reproduce that.
> > >> It can be reproduced in next branch. you can try it in the latest next branch.
> > > Can it be reproduced in 5.5-rc1?
> > >
> > commit 78adcacd4edbd6795e164bbda9a4b2b7e51666a7
> > Author: Stephen Rothwell <sfr@canb.auug.org.au>
> > Date:   Thu Dec 12 15:48:07 2019 +1100
> > 
> >     Add linux-next specific files for 20191212
> > 
> > I  reproduce it  based on this commit.  The related config is attached.
> 
> OK, now I get what's going on. EXTCON is build as a module, but
> FUSB302 is not. This should be explained in the commit message.
> 
> That does not mean we have to force everybody to enable EXTCON in
> order to use this driver. Try something like this:
> 
> diff --git a/drivers/usb/typec/tcpm/Kconfig b/drivers/usb/typec/tcpm/Kconfig
> index 72481bbb2af3..06e026f6325c 100644
> --- a/drivers/usb/typec/tcpm/Kconfig
> +++ b/drivers/usb/typec/tcpm/Kconfig
> @@ -31,6 +31,7 @@ endif # TYPEC_TCPCI
> 
>  config TYPEC_FUSB302
>         tristate "Fairchild FUSB302 Type-C chip driver"
> +       depends on EXTCON=n || EXTCON=y || (EXTCON=m && m)

Ugh.  We need a better "pattern" for stuff like this, it's getting more
and more frequent.

And no, I don't have a better idea :(

thanks,

greg k-h